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We compared the clinical features, laboratory and coronary angiographic findings, treatments, and outcomes among patients with ST-segment elevation myocardial infarction (MI) with and without left bundle branch block (LBBB). We examined 5,742 patients with ST-segment elevation MI with and without LBBB treated with primary percutaneous coronary intervention in the Assessment of Pexelizumab in Acute Myocardial Infarction trial. The main outcome measures were obstructive coronary disease, MI, positive cardiac biomarkers, angiographic Thrombolysis In Myocardial Infarction flow, and death, MI, or congestive heart failure at 90 days. LBBB was present in 98 patients (1.7%). According to the protocol, patients with LBBB were eligible only if they had ≥1 mm concordant ST-segment elevation. Obstructive coronary artery disease was present in >87% of the patients with LBBB. Documented MI (elevated biomarkers) with an initially occluded infarct artery was more common in patients with LBBB with concordant ST-segment elevation (71.4%) than in patients without (44.1%; p = 0.027). The use of ST-segment elevation concordance criteria in the presence of LBBB was more often associated with documented MI with an identifiable culprit vessel with an initially occluded infarct-related artery. In conclusion, because a substantial proportion of patients with LBBB have acute MI with a culprit lesion and positive biomarkers, these data support immediate catheterization with the intent for primary percutaneous coronary intervention for all patients presenting with suspected ST-segment elevation myocardial infarction, ischemic symptoms, and presumed new LBBB, particularly if concordant ST-segment elevation is present.

Guidelines recommend that patients with suggestive symptoms of myocardial ischemia and ST-segment elevation (STE) inor =2 adjacent electrocardiographic leads should receive immediate reperfusion therapy. Novel strategies aimed to reduce door-to-balloon time, such as prehospital wireless electrocardiographic transmission, may be dependent on the interpretation accuracy of the electrocardiogram (ECG) readers. We assessed the ability of experienced electrocardiographers to differentiate among STE, acute STE myocardial infarction (STEMI), and nonischemic STE (NISTE). A total of 116 consecutive ECGs showing STE were studied. Fifteen experienced cardiologists were asked to decide, based on the ECG and assuming that the patient had compatible symptoms, whether they would send each patient for primary percutaneous coronary intervention (PPCI). If NISTE was chosen, the reader selected 1 or more 12 possible options to explain the choice. Of 116 patients, only 8 had STEMI. The percentage of ECGs for which PPCI was recommended for the patient by the individual readers varied widely (7.8% to 33%). There was no significant difference between the North American and Other Countries readers (p = 0.13). The sensitivity and specificity of the individual readers ranged from 50% to 100% (average 75%) and 73% to 97% (average 85%), respectively. There were broad inconsistencies among the readers in the chosen reasons used to classify NISTE. In conclusion, we found wide variations among experienced electrocardiographers in reading ECGs with STE and differentiating STEMI with need for PPCI from NISTE. There is a need to revise our current electrocardiographic criteria for differentiating STEMI from NISTE.

ST-segment depression (ST-D) on the admission electrocardiogram of patients with non-ST-elevation acute coronary syndromes (NSTEACSs) is associated with higher mortality. However, few studies have evaluated the effect of location of ST-D and T-wave polarity on long-term prognosis of patients with NSTEACS. Electrocardiographic (ECG) and clinical data from 6,770 patients with NSTEACS randomly assigned in the Global Use of Strategies to Open Occluded Coronary Arteries (GUSTO) IIB trial were analyzed retrospectively. One-year mortality was correlated with location of ST-D (leads I and aVL; II, III, and aVF; V1 to V3; or V4 to V6) and T-wave polarity. ST-D in any of the ECG locations was associated with higher mortality compared with patients without ST-D. Patients with ST-D and T-wave inversion in leads V4 to V6 had the highest 1-year mortality rate of all groups (16.2%), significantly higher compared with patients with ST-D without T-wave inversion in those leads (9.0%, p=0.001). Logistic regression analysis showed that age, hyperlipidemia, Killip class>I, history of myocardial infarction, history of heart failure, history of angina pectoris, systolic blood pressure, heart rate, sum of ST-D (odds ratio 1.061, 95% confidence interval 1.035 to 1.087, p

There is conflicting evidence with regard to the value of electrocardiographic left ventricular hypertrophy (LVH) in myocardial infarction. Of 5,951 patients in the ASSENT-3 trial, 273 (5%) had LVH on baseline electrocardiograms and had significantly higher mortality rates at 30 days (11% vs 6%, p = 0.001) and 1 year (13% vs 8%, p = 0.007). After adjustment for differences in baseline parameters, LVH remained an independent predictor of 30-day (hazard ratio 2.3, 95% confidence interval 1.4 to 3.9) and 1-year (hazard ratio 1.8, 95% confidence interval 1.1 to 2.8) mortality rates. Thus, electrocardiographic LVH is a prognostic tool in identifying short- and long-term mortality rates in patients who have ST-elevation myocardial infarction and receive fibrinolysis.

The prognostic value of myocardial infarct size estimation by QRS scoring in patients with ST-segment elevation myocardial infarction (STEMI) who undergo primary percutaneous coronary intervention (PCI) is unclear. The standard 32-point Selvester QRS score on the discharge electrocardiogram (each point approximately 3% left ventricular mass) was calculated in 4,113 patients with STEMI who underwent primary PCI and survived to hospital discharge in the APEX-AMI trial. QRS scores were divided into tertiles, i.e.,or =3 (10% myocardium), 4 to 7 (10% to 21% myocardium), andor =8 (21% myocardium). Adjusted associations between QRS score and 90-day outcomes (death and composite of death/congestive heart failure (CHF)/shock) were examined. Higher QRS scores were associated with male gender, higher heart rate, worse Killip class, noninferior infarct location, greater ST-segment deviation, and longer times to reperfusion. Higher QRS scores were also associated with impaired culprit artery flow before and after PCI and more frequent multivessel disease. Adverse outcomes occurred more often in patients with higher QRS scores (90-day death: 1.9%, QRS score 0 to 3; 3.4%, 4 to 7; 4.9%,or =8; 90-day death/shock/CHF: 4.5%, 0-3; 7.8%, 4 to 7; 12.1%,or =8). After multivariable adjustment, patients with higher QRS scores remained more likely to develop an adverse outcome versus those with QRS scoresor =3 (score 4 to 7, hazard ratios [HR] for death 2.08, 95% confidence interval [CI] 1.26 to 3.41; HR for death/CHF/shock 2.00, 95% CI 1.26 to 3.17; scoreor =8, HR for death 2.57, 95% CI 1.56 to 4.24, HR for death/CHF/shock 2.93, 95% CI 1.84 to 4.67). In conclusion, infarct size as estimated by QRS scoring at hospital discharge is an independent and prognostically relevant metric in patients with STEMI undergoing primary PCI.